what is the anatomical position of the kidney?
- sits at T12 to L3
- approximatley 3 vertebrae long
- right one often sits lower due to presence of the liver
- adrenal glands sit immediatley superior to the kidneys
what are the layers of fascia and fat that surrround the kidney (deep to superficial) ?
- renal capsule, tough fibrous layer
- perirenal fat, collection of extraperitoneal fat
- renal fascia, encloses the kidney and suprarenal glands
- pararenal fat, mainly located on the posterolateral aspect of the kidney.
what are the renal pyramids?
where the outter cortex extends into the inner medulla dividing it into triangular shapes, known as the renal pyramids
how does urine drain from the kidney to the ureter?
the renal papilla (apex of renal pyramid) is associated with the minor calyx which collects urine from the pyramids, multiple minor calyx merge to form a major calyx. Urine then passes into the renal pelvis and into the ureter.
where do the renal arteries arise from?
- immediatley from the abdominal aorta, L1-2
- (inferior to origin of superior mesenteric artery)
what is the lymphatic drainage of the kidney?
- lymph from the kidney drains into the lateral aortic (para-aortic) lymph nodes, located at the origin of the renal arteries
Embryologically where does the urogenital system arise from?
- the intermediate mesoderm
what is the utero pelvic junction?
The point at which the renal pelvis narrows to form the ureter
describe the nerve supply to the ureters
Nervous supply to the ureters is delivered via the renal, testicular/ovarian and hypogastric plexuses. Sensory fibres from the ureters enter the spinal cord at T11-L2, with ureteric pain referred to those dermatomal areas.
what are the 5 segments of the kidney?
1) Apical/Superior
2) Caudal/Inferior
3) Anterior Superior
4) Anterior Inferior
5) Posterior
what are the 3 main places where water reabsorption occurs in the kidney?
the proximal convoluted tubule (PCT), the descending limb of the Loop of Henle and the collecting ducts.
describe the process of water filtration and water absorption in the kidney (reabsorption at each part of nephron)?
1) glomerelus filters small solutes from the blood
2) proximal convuluted tubule, reabsorbtion of ions, water and nutrients
3) descending loop of henle, aquaporins allow water to be reabsorbed
4) ascending loop of henle, reabsorbtion of Na+ and Cl-
5) distal tubule, selective reabsorption to maintain pH and electrolyte balance
6) collecting duct, reabsorbs solutes and water from the filtrate
explain the process of filtration in the glomerelus
- Visceral epithelium covers glomerular capillaries inside Bowman’s capsule.
- one cell thick and has podocytes
- pedicles are projections of the podocytes
- for things to filter through it must fit through the pedicles
- high pressure in glomerelus is formed from the afferent arteriole having a larger diameter than the efferent arteriole
what is the vasa recta?
the efferent arteriole from the glomerelus, forms the vasa recta which is capillaries which follow the route of the nephron to allow for reabsorption
how does reabsorption occur in the proximal convuluted tubule?
- Na+ is absorbed along with glucose or amino acid, the glucose or amino acid is then reabsorbed back into circulation
- Na+ and H+ co-transporter moves Na+ out and H+ in. Na+ is reabsorbed into blood through Na+/K+ ATPase (on basal aspect of cell)
- in the lumen H+ + HCO3- -> H2CO3
- carbonic anhydrase forms H2O and CO2 from H2CO3, this then passes into the cell where the reverse reaction occurs
- H2CO3 is able to dissociate back to H+ and HCO3- and the H+ is used in the Na+/H+ transporter for the cycle to continue
How does the proximal convuluted tubule play a role in maintaining blood pH?
HCO3- is reabsorped into the blood through a sodium dependent cotransporter
How does re absorption occur in the ascending limb of the loop of henle?
- K+, 2Cl- and Na+ transporter on apical cell membrane
- 2Cl, K+ enter circulation through a transporter in basolateral membarne
- Na+ enters circulation through Na+/K+ ATPase
- free channels moving Na+ out of lumen and K+ into lumen
reabsorption in the distal tubule?
- Cl- reabsorbed through chloride channels
- Na+ reabsorbed through Na+/K+ ATPase
- Mg2+ and Ca2+ are reabsorbed through diffusion in paracellular routes
reabsorption in the distal CT and the collecting duct?
- Na+, H+ transporter allows for Na+ to be reabsorbed and H+ to enter lumen
- carbonate ions are reabsorbed through a carbonate chloride exchanger
- aldosterone control Na+/ K+ exchanger
where is aldosterone secreted from?
- adrenal glands, specifically adrenal cortex
- in response to low blood pressure
what are the effects of increased aldosterone on the nephron?
- more Na+ reabsorbed
- more water reabsorbed
- this will mean more K+ is secreted (into lumen)
what is the mascula densa?
Macula densa cells in the distal nephron, according to the classic paradigm, are salt sensors that generate paracrine chemical signals in the juxtaglomerular apparatus to control vital kidney functions, including renal blood flow, glomerular filtration, and renin release.
synthesis of vitamin D
in the skin: 7- dehydrocholestrol
+UV
in the blood: cholecalciferol (Vit D3)
in the liver: 25-hydroxylase (enzyme) , forms
25-hydroxycholecalciferol (aka calcifedoil)
in the kidney: 1- alpha hydroxylase (enzyme),
forms 1,25- hydroxycholecalciferol (aka calcitriol)
